In theaters and concert halls it is frequently necessary to have a portion of the stage which can be raised or lowered for special scenic effects. In one known application, the front part of the stage is raised to increase the total area as needed, and lowered to accomodate, for example, an orchestra in the pit thereby made. If the stage is already large enough without the extra area of the movable portion the latter can remain in lowered position and extra seats for a performance may be added thereover.
U.S. Pat. No. 3,399,887 to W. Altier, dated Sept. 3, 1968 provides a stage lift consisting of conventional hydraulic rams which, because of their length, must be partially embedded in the ground; such rams are also difficult to control and synchronize.